title: What data are available on the extent of illicit drug use and dependence globally? Results of four systematic reviews.
abstract: BACKGROUND
  We systematically reviewed availability and quality of data on the prevalence of use and dependence on meth/amphetamine, cannabis, cocaine and opioids.
  
  
  METHODS
  Multiple search strategies: (a) peer-reviewed literature searches (1990-2008) using methods recommended by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group; (b) systematic searches of online databases; (c) Internet searches to find other published evidence of drug use; (d) repeated consultation and feedback from experts around the globe; (e) a viral email sent to lists of researchers in the illicit drug and HIV fields. Data were extracted and graded according to predefined variables reflecting quality of data source.
  
  
  RESULTS
  Qualitative evidence of illicit drug use and dependence was found for most countries, which hold over 98% of the world's population aged 15-64 years. Countries where use was identified but prevalence estimates had not been made (evidence of drug supply, trafficking, reports of use, treatment data) were mainly from Asia, Africa, the Middle East, and Oceania. Estimates of the prevalence of use were located in 77 countries for meth/amphetamine, 95 for cannabis, 86 for cocaine and 89 for opioids. Dependence prevalence estimates existed in very few countries; 9 meth/amphetamine dependence estimates, 7 cannabis dependence estimates, 5 cocaine dependence estimates, and 25 opioid dependence estimates were located.
  
  
  CONCLUSIONS
  Data on the extent of meth/amphetamine, cannabis, cocaine and opioid use and dependence must be improved in quality and coverage. Dependence estimates are lacking even in high income countries that have required resources. Responses to illicit drug dependence require better estimates of its scale.
authors.affiliation: Burnet Research Institute, GPO Box 2284, Melbourne, Victoria 3001, Australia. louisa@burnet.edu.au
authors.forename: Louisa
authors.initials: L
authors.lastname: Degenhardt
authors.forename: Chiara
authors.initials: C
authors.lastname: Bucello
authors.forename: Bianca
authors.initials: B
authors.lastname: Calabria
authors.forename: Paul
authors.initials: P
authors.lastname: Nelson
authors.forename: Anna
authors.initials: A
authors.lastname: Roberts
authors.forename: Wayne
authors.initials: W
authors.lastname: Hall
authors.forename: Michael
authors.initials: M
authors.lastname: Lynskey
authors.forename: Lucas
authors.initials: L
authors.lastname: Wiessing
authors.forename: Maria Elena Medina
authors.initials: ME
authors.lastname: Mora
authors.forename: Nico
authors.initials: N
authors.lastname: Clark
authors.forename: Johanna
authors.initials: J
authors.lastname: Thomas
authors.forename: Christina
authors.initials: C
authors.lastname: Briegleb
authors.forename: Jennifer
authors.initials: J
authors.lastname: McLaren
mesh_terms: D057225:Data Mining; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D012107:Research Design / Q000706:statistics & numerical data*; D019966:Substance-Related Disorders / Q000453:epidemiology*
chemical_list: D013287:Illicit Drugs